We studied Bacillus subtills transaiptional regulators containing Helix Tum-Helix (HTH) motif in the molecule and those that affect expression of aprE, the gene encoding extracellular alkaline protease. The strategy we adopted was that we fist carried out microarray analysis, and if any difference was detected in expression levels, we then confirmed the result using a lacZ gene fusion. For transaiptional regulator AhrC(HTH), we found that in addition to the known targets of the factor it affected expression of pucR, the negative regulator of the genes involved in purine degradation. It was also found that AhrC negatively affected the expression of aprE and both the ure operon and rgA that are under the control of GlnA. Since it appears that AhrC, GlnA and AprE are closely related in the supply of the nitrogen source, it can be assumed that they form a network in the cell. For ComK(HTH), we found many target genes in addition to those involved in competence development, and recognized the known consensus sequence in the regions upstream of the codng regions. For AnsR and DeoR, which contain HTH, we could not find genes other than their already known targets. We also investigated the regulator, YclJ, of a two-component system, and found that it controls at least three operons. Alignment of the sequences in the upstream regions of the operons and deletion analysis allowed us to identify a consensus sequence to which YclJ binds.We also studied SenS that contains HTH in the molecule and positively regulates aptE expression. It was shown that SenS exerted a negative effect on the transcription of scoC, an inhibitor of aprE expression. Furthermore, we found that a deletion of ybaL (salA) whose function had been unknown resulted in a decrease in aprE expression and that SalA was a positive regulator of scoC expression.